Transmission of pictures by electricity



Nov. 23 ,1926.

H. E. IVES TRANSMISSION OF PICTURES BY ELECTRICITY Filed Sept. 24, 1924Fig/ Patented Nov. 23, 1926.

UNITED STATES PATENT OFFICE.

HERBERT E. IVES, MONTCLAIR, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRICCOMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TRANSMISSION OF PICTURES BY ELECTRICITY.

Application filed September 24, 1924. Serial No. 739,525.

This invention relates to the transmission of pictures, writing, etc.,by electricity and, more especially, it relates to a novel arrangementfor reproducing a picture particularly suitable for printing by thestereotype process.

In a copending applicationof H. E. Ives, Serial No. 711,755, filed May8, 1924, a system for efl'ecting the transmission of pictures byelectricity in an eflicient and practical manner is disclosed. Accordingto this system, the characteristics of the picture are transmitted asimpulses of a voice frequency carrier Wave es ecially adaptable to transmission over or inary telephone lines or circuits. The modulated wavesare received at a distant station and eifect the operation of a lightcontrolling valve which causes the exposure of a photosensitive surfacein accordance with the tone value of elemental areas of the picture. Thepicture is thus reproduced on this sensitive surface in the form of aplurality of parallel lines of uniform density and varying width. In thereproduction of pictures suitable for news print work, it is necessary,even in the totally white areas of the picture, to provide a printingstructure. This, according to the invention covered in the previouslyrefer 'ed' to application, results from the formationv of thin. narrowlines over such areas. However, when such pictures are reproduced onnews print paper by the stereotype process, these thin lines arefrequently. so broadened that the white portions of the picture appeartoo gray and the reproduced picture consequently lacks contrast.

It is the principal object of the present invention to accomplish thetransmission of" pictures by electricity in a practical manner andeffect the reproduction of the pic- .tures in a form especially suitablefor news print reproductions. I

In one embodiment of the invention, the characteristics of the picture,which are transmitted as impulses of a voice frequency current wave to adistant station over ordinary telepho'ne'lines, are reproduced at thedistant station on a photosensitive surface not as continuous parallellines of uniform density and varying width, but as broken lines ofuniform density and varying width. Between the breaks in the lines dotsof pre arranged dimensions are formed automatically, thereby providing astructure which is through an aperture in a screen 1.

particularly adapted to news print work.

These dots appear only in the portions of L cated at the receivingterminal for repr0-' ducing the characteristics of the picture astransmitted through the apparatus and circuits of Fig. 1; Fig. 3 shows arinting structure of a picture as reproduced by the method disclosed inthe previously referred to application; Fig. 4 shows the printingstructure produced in accordance with the embodiment of the presentinvention.

Referring for a moment to Fig. 1, a modulator 13 is supplied withcarrier waves from an alternating current source 12 and with picturecurrent from a photo-electric cell 8 and a picture amplifier 2.Modulated carrier Waves from the modulator 13 are impressed upon thetransmission line 14 which extends between two-remotely situatedstations through a filter SPF. The photo-electric cell 8 is locatedwithin a transparent drum 4 which is driven in any suitable manner byshaft 3 to which power is communicated. Mounted on the drum 4 is atransparency'5 of the picture, the characteristics of which are to betransmitted. Light from an incandescent source 6 is focused by means ofa lens 7 on the photo-electric celi hB e amount of light affecting thephoto-electric cell 8 is determined by the tone value or density of theelemental. area of the transparency 5 which is, at'that instant,adjacent to the a erture in the screen'l at the focal point 0 the lightbeam. The amount of light within the photo-electric cell 8 in turndetermines the amount of'current which can flow from the battery 9 tothe photo-electric cell 8 and resistance 10. Consequently, the potentialdrop across the resistance 10 is applied to the input circuit of thepicture amplifier 2. The am lified current determined y the amount ofight affecting the photoelectric cell 8 is impressed upon the modulator13 by resistance 11 simultaneously with carrier current fi'om thecurrent source 12.1 Accordin 1y, modulated current waves from the moduator 13 are im ressed upon th line 14 through the filter PF.

Coming now to the receiving arrangement shown in Fig. 2; the modulatedcarrie'r waves from the line 14, after passing through the filter RPF,are impressed on an amplifier set RA and thence to theoperating wire '18of a light valve 16 through a suitable transformer. 15. The operatingwire 18 is suspended in a magnetic field produced by magnet 19 and isarranged to vibrate in a direction transverse to the plane of the paper.For further details with reference to the construction and character 'ofoperation of the light valve 16, reference should be had to copendingapplication of E. C. Wente filed May 1, 1923, Serial No. 635,886. Lightfrom the source 20 is directed by means of lens 21 upon the conductor18. Preferably, the light source 20 is an incandescent lam with spiralfilaments arranged coaxially wlth the lens 21 so that the apertureforming elements of the light valve 16 are intensely and uniformlyilluminated. The operating conductor '18 is one of these apertureforming elements. The screen 25 is another. It is, of course, understoodthat these members or elements may be so located as to roduce a noexposure condition.

Lig t from the source 20 in turn controlled by; the light valve 16passes through a lens 22 and exposes a photosensitive surface 24 carriedby a drum 23. The drum 23, like the drum 4 located at the transmittingstation, is adapted to be rotated for bringing the various elementalareas of the photosensitive surface 24 in alignment with the image ofthe aperture in screen 25.

Interposed between the light valve 16 and the lens 22 is a transparentmirror 26 which allows the passage of the light rays from the source 20as determined by the operation of the light valve 16. Arranged inoperative relation with respect to the transparent mirror 26 is anauxiliary light source'27 of the same character'as the light source 20.

Light beams from the light source 27 are directed on the mirror 26through a lens 28 and a screen 29, in which is an aperture whose opticaldistance from the drum 23 is .the same as that of the aperture in screen25. Located adjacent to the screen 29 is a sectored disc 30 whichfunctions to break up the light impressed from the light source 27 onthe transparent mirror 26 and, in conse uence, the photosensitivesurface 24.

he photosensitive surface 24is such that it is exposed to full depth bya single exposure to light from either light source 20 or light source27. Additional ex osures of the same area have no effect to c ange thistone value. Thus, the developed recordv currents produced by theoperation of the photo-electric cell 8 in accordance with the elementaltone value or density of the transparency 5 be so adjusted that forpractically white areas no current be impressed on the modulator 13.Thus, at the receivin station, the light valve 16 will be close and,consequently, no light is impressed on the photosensitive surface 24from the light source 20. During this period, however, light from theauxiliarysource 27 is applied.

through the sectored disc 30 and reflected by the transparent mirror 26to the photosensitive surface 24.. The exposure of the photosensitivesurface due to the use of the sectored disc 30, results in a series ofimages of the aperture in screen 29, forming dots of uniform size anddensity as shown in Fig. 4. By omitting the sector disc 30, theauxiliary source of light 27 may be made to expose the photosensitivesurface to produce a thin narrow line which may be sufiicient forcertain purposes.

For the transmission of pictures, the arrangements of Figs. 1 and 2 areconnected by the telephone line 14. The. drums 4 and 23, located at thetransmitting and wwwated in accordance with the impressed currents forallowing light from the light source 20 to expose the photosensitivesur' face 24 in accordance with the elemental tone value on density ofthe transparency 5. In the case of white areas appearing in thetransparency 5, the current is so adjusted that the light valve 16 ismaintained closed when the photo-electric cell 8 is adjacent to theseareas. The photosensitive surface 24 will, however, be exposed toreproduce dots in the form shown in Fig. 4 due to the application oflight through the sectored disc and the transparent mirror 26 from .thelight source 27. The photosensitive surface will, thus, be exposed, butthe dots -\produced by the sectored disc 30 will be submerged by thelines whenever the width of the line is greater than the size of thedots, v

The invention has been shown and described as applied to a particularsystem, but it is obvious that it may be applied to other systems withequally good results. It is, therefore, not intended that the inventionshould be limited to the particular arrangement disclosed. y I

What is claimed is:

1., In a system for transmission of pictures by electricity, means tomodulate a carrier wave in accordance with the tone value of theelemental areas of the picture, a light controlling valve,'1mean s toimpress said modulated current on said light controlling valve, 9.photosensitive surface exposed in accordance with the tone values of theelemental areas of said picture asdetermined by the operation of saidlight controlling valve an auxiliary optical system fonex 0sing saidphotosensitive surface to .-pro uce dots in the white areas comprisingatransparent mirror through'which light rayslcontrolled by said lightcontrolling valve pass, an auxiliary-source of light reflected by 'saidmirror on said hotosensitive surface, and means for breaking said lightupinto dots. '2. i'na system for transmission of pictures byelectricity, means'to modulate a carrier wave in accordance with thetone value of the elemental areas of the picture, a light controllingvalve, means to impress said modulated current on said light controllingvalve, a photosensitive surface ex osed in accordance with the tonevalues 0 the elemental areas of said picture 'as determined by theoperation of said light controlling valve, an auxiliary optical systemfor exposing said photosensitive surface to produce dots in thewhiteareas comprising a transparent mirror through which light rayscontrolled by said light controlling valve pass, the auxiliary source oflight reflected'by said mirror on said hotosensitive surface, and asectored disc' or breakingup said light into idots; v

-3. In a system for the transmission of pietures by electricity, areproducing element, a transparent mirror, a source for producing a beamof .lightjmeans for directing the beam of light through said mirror tothe surface of said element. alight valve actualed in accordance withthe transmitted picture currents for controlling said beam of light toexpose the reproducing element/in accordance with the tone values of theoriginal picture, a second source of light,imeans for directing a beamfrom said second source to the surface of the mirror, said ,mirrorserving to reflect said second beam to the surface of said element,'andmeans for controlling said second beam in such a manner that a uniformdot pattern 1s secured throughout the area of said reproducing ele-.ment.

4. ha system for the transmission of pictures' by electricity. asensitized reproducin element, a source for producing a'beam o light,astationary transparent mirror, lenses for directing said beam throughsaid mirror and to the surface ofsaid element, a light valve responsiveto picture currents for controlling :said beam to reproduce the tonevalues of the picture on said element. a second source for producing abeam of light, means for directing said second beam to the surface ofsaid mirror, said mirror'serving to reflectthe second beam to thesurface of said element, and a rotating disctacting upon said secondbeam to cause a uniform dot pattern to be superposed upon saidreproducing element.

In witness whereof, I- hereunto subscribe my name this 18th day 'ofSeptember, A. D.- 1924. l

1 HERBERT E. ivns;

